Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/17699
Title: Transport Properties of Concrete with Lightweight Aggregates
Authors: LIU XUEMEI
Keywords: Absorption, Chloride, Concrete, Diffusion,Interface transition zone, Internal curing,Lightweight aggregate, Migration,Permeability,Porosity,Sorptivity
Issue Date: 17-Dec-2009
Source: LIU XUEMEI (2009-12-17). Transport Properties of Concrete with Lightweight Aggregates. ScholarBank@NUS Repository.
Abstract: Literature review indicates that information on the transport properties of concrete with lightweight aggregate (LWA) for internal curing is limited. There are also contradicting opinions on the effect of LWA on the transport properties of concrete. In addition, there is a lack of information for predicting the transport properties of lightweight concrete (LWC). For structures exposed to severe environment, such information is essential. Therefore, this research is carried out. This research investigates the effect of LWA on transport properties of concrete including water absorption, water permeability, and resistance to chloride ion penetration. It covers normal weight concretes (NWCs) in which LWA is used for internal curing, LWC where only coarse LWA is used, and LWC where all aggregates are lightweight. Effects of the cumulative LWA content, porosities and surface textures of LWA, and w/c of concrete on the transport properties of concrete are also investigated. Control NWCs and concrete with a shrinkage reducing admixture are also included for relative comparisons. Rapid chloride penetrability test (ASTM C 1202), rapid migration test (NT Build 492), and salt ponding test (AASHTO T 259) are conducted to evaluate the concrete resistance to chloride-ion penetration. In general, concretes with LWA had water absorption and permeability similar to or lower than those of the NWC and concrete with shrinkage reducing admixture (SRA) with the same w/c 0.38. The charges passed, chloride migration coefficient and chloride diffusion coefficient of such concretes were in the same order as those of the NWC and the concrete with SRA. When high-performance lightweight concrete, shrinkage reducing admixture or pre-soaked LWA can be used to reduce/eliminate autogenous shrinkage of concrete. Comparing LWAs of different sizes for internal curing, the increase in the more porous crushed lightweight particles in concrete seems to increase the penetration of chloride ions in the concrete. The resistance of LWC to chloride ion penetration decreased with increase in the cumulative LWA content. The water penetration depth under pressure and water sorptivity showed, in general, similar trends. The increase in porosity of coarse LWA in concrete increased the sorptivity and permeability slightly compared to NWC of similar w/c. Fine LWA has more influence on the transport properties of concrete than coarse ones. For a given type of LWA, coarse LWA did not influence the water sorptivity and permeability significantly compared to NWC of similar w/c and mix proportion. Fine LWA has more influence on the transport properties than coarse LWA. For given size and content of coarse LWA, the more porous coarse LWA tends to reduce the resistance to water and chloride ion penetration of concrete. In addition, LWC with very low unit weight about 1300 kg/m3 but high resistance to water and chloride ion penetration was developed by using low w/cm, silica fume, and LWA with very low density. Such low unit weight has opened up a new avenue for potential use of LWC in marine environment for floating structures. Based on the experimental results and regression analyses, empirical relationships of sorptivity, charge passed, and chloride migration coefficient versus the water accessible porosity and oven dry unit weight of the concrete are established. For both LWC and NWC, physical properties of water accessible porosity and unit weight can be easily determined in the laboratory. Using the empirical equations, the transport properties of concrete can be estimated for quality control and for estimating durability of concrete.
URI: http://scholarbank.nus.edu.sg/handle/10635/17699
Appears in Collections:Ph.D Theses (Open)

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